Thomas Lord Associate Professor in Materials Science
MIT Department of Materials Science and Engineering
We have developed a new type of nanowire-based solar cells that are based on organic/inorganic hybrid device structures and demonstrated two distinct hybrid BHJ architectures with enhanced power conversion efficiencies. The first device structure was composed of GaAs nanowires blended with a conjugated polymer poly(3-hexylthiophene) (P3HT) to form a uniform film consisting of dispersed nanowires in a polymer matrix. We observed that above a certain nanowire loading threshold, the nanowires facilitate P3HT molecular ordering, which leads to improved charge transport and yields devices with >2.3% power conversion efficiency. In the second device structure, CdS quantum dots were bound onto crystalline P3HT nanowires through solvent-assisted grafting and ligand exchange, leading to controlled organic-inorganic phase separation and an improved maximum power conversion efficiency of 4.1%.
In both cases, our results clearly demonstrate some of the benefits of organic-inorganic BHJ devices, mostly through enhanced absorption and improved carrier transport in the active region of the device. We have also identified several critical parameters to further boost the device efficiency and enable scalable, cost-efficient production, and these will be discussed.